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Re: JFC-Bloodiest Battle ??
"but inventing a niche that does not currently exist is an extraordinary
claim, and requires comensurate levels of evidence."
What, pray tell, is the modern day niche equivalent of therezinosauroids
and Mononykus and its relatives?
options are viable, even if it is difficult to distinguish between
them morphologically. <<<
My point is that the default should not be active predation -- other
Sorry, I have to disagree with Dan. In the absence of any terrestrial
carnivores that are not active predators, the burden of evidence has
to be on advocates to show that it's even energetically possible. Of
course it's entirely possible that dinosaurs (or other extinct
organisms) filled niches that are empty today, but inventing a niche
that does not currently exist is an extraordinary claim, and requires
comensurate levels of evidence. Furthermore, if support for such a
niche is possible, then we would need to evaluate osteological
correlates on a species by species basis.
Given the excellent finite-element analysis done on allosaur skulls,
whose interpretted slash and rake attack style has been corroborated
by recent phylogenetically constrained muscle restorations, there
seems little reason to speculate that allosaurs filled an ecological
niche that does not exist in current ecosystems.
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333
From: Dan Chure <email@example.com>
Cc: DML <firstname.lastname@example.org>
Sent: Fri, 22 Aug 2008 2:44 pm
Subject: Re: JFC-Bloodiest Battle ??
I agree. I admit it is arm waving. My point is that the default should
not be active predation -- other options are viable, even if it is
difficult to distinguish between them morphologically. Varanoids have
low wide skulls, crudely like that of crocodilians (for the sake of
this argument). Allosaurus and a number of other large headed
theropods have extremely narrow preorbital regions, quite in contrast
to varanoids. Take a look at the dorsal view of the skull of
Monolophosaurus or Sinraptor. While vertical loads might be
accommodated, I am less certain about resistance to torque along the
long axis of the preorbital region, especially given all the pneumatic
penetration of the region.
Given the lack of similarity between theropods and living terrestrial
vertebrates, it would not surprise me that they are making livings in
ways unlike anything around now, including a life based primarily on
scavenging. As Peter Dodson once wrote "let dinosaurs be dinosaurs."
Mike Habib wrote:
>> narrow preorbital region. All three are like a pair of scissors and
>> quite unlike Tyrannosaurus with arched and fused nasals. I doubt >>
Allosaurus was capable of sustaining great stresses, especially given
>> the extensive pneumatic system enclosed in the narrow skull. Given
>> the abundance of Morrison sauropo
Allosaurus, like Sinraptor and Monolophosaurus, has an exceedingly
ds, Allosaurus might have been >> primarily a scavenger, rather than a
predator, although that is >> pretty much am waving. Jurassic
Scavenger Club anyone?
An open skull construction need not mean that the maximum loads are >
low - depending on the particular strain distribution, a kinetic skull
> can often take fairly substantial loads without failure. A more >
heavily built skull may indeed be stronger still, but I would be >
hesitant to assume that a more open, mobile skull morphology entails >
carrion feeding. Varanids, for example, have a very open skull >
construction, with a high degree of cranial kinesis, and yet are >
active predators of a range of prey items.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
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